Wide range thermostat



Sept. 6, 1955 E. BLETZ 2,717289 W IDE RANGE THERMOSTAT Filed D80. 17, 1952 IN VEN TOR.

BY EDWARD BLETZ United States Patent O 1 2,717,289 WIDE BANGE THERMOSTAT Edward Bletz, Lexington, Ohio, assignor to Stevens Manufacturing Company, Inc., a corporation 01 Ohio Application December 17, 1952, Serial N0. 326,503 16 Claixns. (C1. 200138) The invention relates in general to thermostats and mme particularly to a resilient member in a thermostat which may have a wide range of adjustment. This application is a continuation-in-part of rny application Serial N0. 207,382, filed January 23, 1951, now Pat. N0. 2,692,317, entitled Snap-Acting Thermostat wherein a resilient strip member co-operates in a therrnostat With a snap-acting strip member. In such prior art form cf snap-acting thermostat a bimetallic strip urged one end of a first strip in a first direction and an adjustable screw urged the middle of the first strip in the opposite direction. T he adjustable screw established the operating temperature for opening and closing contacts carried on the fi;st strip and n a snap-acting strip. When the adjusting screw was adjusted for a temperature near the upper temperature limit of the thermostat and the electrical device controlled by such thermostat reached such temperature thefirst strip would have a considerable deflection. Then if the adjusting screw were adjusted for a temperature near the lower temperature limit of the rhermostat, the first strip would have an even greater deflection which approached the elastic limit cf such first strip, especially under the high ambient temperature comditions of the thermostat. This great stress applied to the first strip under high temperature conditions would in many cases establish a permanent set in this first strip so that upon subsequent return to the high temperature operating conditions of the thermostat, the calibration of 'r'ne thennostat was found to be in error by from ten to thirty degrees compared with the former calibration.

An cbject of the present invention is therefore to provide a thermostat structure which will retain the original calibration throughout the life of the thermostat and despite changes in the adjustment of the adjusting screw at any and all operating temperatures.

Another object cf the invention is to provide a thermosaat which is adjustable in operating temperature over a wide range.

Still another object of the invention is to provide a thermostat which has a Wide range of temperature settings and which may be set for one extreme of the operating range when the ambient temperature is at the other extreme cf the operating range without damage to the thermcstat and further Without change in the calibration cf the thermostat.

Another object of the invention is to provide a thermostat having a cornposite resilient member.

Still another object of the invention is to provide a therrncstat having first and second portions on a resilient member.

Still another object of the invention is to provide a thermostat having a secondary resilient deflectable membi attached to a primary resilient deflectable member.

Still another object of the invention is to provide a thermostat which includes a secondary resilient deflectable member on a strip which is subjected to plural load forces.

Otber objects and a fuller understanding of this invention may be had by referring t0 the following description and claims, taken in conjunction With the accompanyings, in which:

Figure 1 is a plan view of a resilient strip used in the therrncstat;

Fiure 2 is a side view of the strip of Figure 1;

Figure 3 is a side view of a complete therrnostat incc-rporacing the strip of Figures 1 and 2 and set at a low operating temperature;

2717,289 Patented Sept. 6, 1955 Fignne 4 is similar to Figure 3 but Shows the temperature at an upper temperature lin1it;

Figure 1 is a side view like Figure 4 but With the ambient temperature at the upper temperature limit;

Figure 6 is a side view like Figure 3 but With the thermostat readjusted for a low operating temperature.

The Figures 3 to 6 show a side view of the complete thermostat which includes a base 15 and a stack 16. A nut 17 is fastened to the base 15, and this nut includes a stop portion 18. An adjustable screw 20 is threadable in the nut 17, and this screw carries a stop lug 22 for co-operation With the stop Portion 18. The screw 20 carries an insulating tip 23 which is adjusted axially by rotation cf the screw 20.

The stack 16 carries an over center spring member 24, a flexible contact strip 71, and a flexible bimetallic strip 26. A terminal 27 is carried in the stack 16 and is in electrical contact with the spring member 24, and a terminal 28 is likewise carried in the stack in electrical contact With the flexible contact strip 71. A hollow rivet 29 holds together the Stack 16 which includes insulating washers 30 between the various strips.

The over center spring member 24 includes a compression spring strip 32 and a tension spring strip 33 to make this over center spring member 24 a snap-acting device which will snap to alternate positions 0n either side of a neutral center position.

The spring mernber 24 carries a contact 40, and the flexible contact strip 71 carries a contact 41 for co-operation with the contact 40. The flexible contact strip 71 is provided with a U-shaped portion 42 which has a threaded aperture 43. An adjusting screw 44 is threaded in the aperture 43 and carries an insulating tip 45 for establishing the spacing between contacts 40 and 41 in the oft position thereof. An insulating button 46 is carried by the flexible bimetallic strip 26 and is positioned to abut the under side of the contact strip 71 to urge sarne upwardly f0r ambient temperature changes in a given direction.

The flexible contact strip 71 is provided With a small aperture 53. A tongue 52 is provided 011 an insulating spacer 51. This tongue 52 is receivable within the aperture 53 With the insulating spacer 51 positioned between the flexible contact strip 71 and the compression spring strip 32. The insulating spacer 51 has suflicient height to bear against the under side cf the compression spring strip 32 and bow the same upwardly even though the insulating tip 23 is raised to its upper limit as shown in Figure 4.

The Figures 1 and 2 show the flexible contact strip 71 as it is manufactured and ready to be fastened in the stack 16 as part of the complete thermostat. This strip 71 has a curved slot 72 positioned toward the contact and surrounding approximately 200 of arc of the apertun: 53. The slot 72 and the aperture 53 establish a U-shaped resilient member 73. The strip 71 as best seen in Figure 2 is bent in a given direction to a permanent set of approximately 15 along a line 74 adjacent the mounting end of the strip 71. The contact strip 71 is further bent in the opposite direction to a permanent set of approximately 5 along the line 75 which substantially intersects the aperture 53. Such last mentioned permanent set does not include the U-shaped resilient member 73 as best seen in Figure 2.

Operation The Figure 3 shows the thermostat adjusted for a low temperature near the low limit of operation of the thermostat. In this position the insulating tip 23 is axially moved downward by the adjustable screw 20. The insulating tip 23 acts through the compression spring strip 32 directly upon the insulating spacer 51 and thus bows downwardly the contact strip 71. The contacts 40 and 41 are shown in their closed position.

The Figure 4 shows the thermostat with the insulating tip 23 moved upwardly to establish the thermostat near the upper limit f the operating range. In this position the natural resiliency of the contact strip 71 causes it to be bowed upwardly holding the insulating spacer 51 against the compression spring strip 32. The contacts 40 and 41 are again shown in their closed position. Further, the bimetallic strip 26 is shown in the undeflected position as it would be for room temperature conditions.

The Figure shows the thermostat adjusted for the same temperature as in Figure 4; however, the bimetallic strip, 26 is now shown in its heated position With the contacts 40 and 41 open. This thermostat could be usec l in an electrical appliance such as a flatiron which would have an operating temperature range, for example, from 70 F. to 550 F. Wllh the terminals 27 and 28 connected to a source of electrical energy and the beating element of the flatiron and With the thermostat within the flatiron, the ambient temperature of the thermostat could be between 70 F. and 550 F. The Figure 5 shows the thermostat with the bimetallic strip 26 defiected as by heat of approximately 550 F. It would be noted that the contaet strip 71 is bent upwardly at the end into a consiclerable curvature.

The Figure 6 shows the thermostat still under ambient temperature conditions of 550 F. but With the adjusting screw 20 readjusted by the operator to a posi tion near the W operating temperature liniit. Figure 6 thus shows that with the insulating tip 23 moved downwardly the contact strip 71 is bowed even more than in Figure 5. The U-shaped resilient member 73 is now deflected below the plane of the contact strip 71 rather than being deflected above as in Figure 2. The prior art form of thermostat was found to have the calibration thereof destroyed by a change of adjustment in the adjust ing screw such as that shown in the change frorn Figure 5 to Figure 6. With the incorporation of the U-shaped resilient member axial acljustments of the insulating tip 23 cause flexing, of the resilient member 73 Which will in turn transmit it to the contact strip 71. With this resilient member 73, which may be considered a secondary resilient member, attached to the prirnary resilient member 71, the thermostat may be adjusted frorn a high operating temperature to a 10W operating temperature wit h the ambient at a high temperature without damage to the thermostat and without change in the calibration 0f the thermostat. The U-shaped slot 51 also relieves the stress in the contaet strip 71 when it is greatly deflected or bent by the insulating tip 23. Both the prirnary resilient mernber 71 and secondary resilient member 73 are flexible strips er members Which may be ealled creep-aetion mernbers, that is, they have a generally linear relationship 0f force versus deflection.

Although t his invention has been described in its preferred form With a certain degree 0f particularity, it is und erstood that the present disclosure of the preferred form has been made only by way or" example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter clairned.

What is claimed is:

l. In a therrn0stat, a primary resilient member having first, second, and third portions, said first portion adapte d to be fastened in said thermostat, a secondary resilient member integral with the second portion cf said primary member, said seconclary member adapted to be deflected in a first direction to thus bend said primary rnember about said first portion, said third portion of said prirnary member adapted t0 be deflected in the opposite direction to bend sarne substantially at said second portion.

2 A contact carrying blade for a thermostat, comprisiflg, 21 resilient strip of metal having a mounting end an cl a contact end, said mounting end adapted to be III fastened in a stack of a thermostat for co-operation therewith, said strip having a weakened portion to thus define a U-shaped secondary resilient member at the mid-portion of said strip, said Ushaped member adapted to be abutted by an adjustable member to place an adjustable load in a first direction on said U-shaped member t0 bend same and thus bend said strip about said mounting end, said contact end of said strip adapted to have an adjustable load placed thereon in an opposite direction to bend said strip substantially at said adjustable member.

3. A contact carrying blade for a thermostat, comprising, a resilient strip of metal having, a mounting end and a contact end, said mounting end adapted to be fastened in a stack of a thermostat for co-operation therewith, a U-shaped secondary resilient member at the mid-portion of said strip defined by a U-shaped slot, said U-shaped member adapted to be abutted by an adjustable member to place an adjustable load in a first direction on said U-shaped member to bend same and thus bend said strip abut said mounting end, said contact end of said strip adapted to have an adjusrable lozrl placed thereon in an opposite direction to bend said strip substantially at said adjustable member.

4. A contact carrying blade for a thermostat, comprising, a resilient strip of metal having a mounting end and a eontact end, said mounting end adapted to be fastened in a stack of a thermostat for co-operation therewith, a U-shaped secondary resilient member at the mid-portion of said strip defined by a U-shaped slot and extending toward said contact end, said U-shaped memher adapted to be abutted by an adjustable member to place an adjustable load 011 said U-shaped member in a first direction to bend said U-shaped member and thus bend said strip about said mounting end, said contact end 0f said strip adapted to have an adjustable load placed thereon in the opposite direction with the fulerurn of said strip being substantially at said adjustable rnember.

5. A contact carrying blade for a thermostat, comprising, a resili ent strip of metal having a mounting end and a contac t engl, said mounting end adapted t0 be fastened in a stack of a thermostaffor ccoperation therewith, said strip being bent in a first direction to a permanent set offa srnall angle along a first line adjacent said mounting and, a U-shped secondary resilient memoer at the mid-portion of said strip defined by a U-shaped slot and extending toward said contact end, said strip being bent in the Opposite direction to a permanent set er" a second small angle alqng a second line at about the micl-point of said strip, said last mentioned permanent sei excluding said U-shaped member, said 'U-shaped member adapted to be abur'ted by an adjustable member to place an acljusta'ole load on said LLshaped mernber in said epposite direction to bend said U-shaped rnembez about said second line and thus bend said strip about said first line said contact end of said strip adapted to have an adjustable lead placed there0n in said first directi0n with the fulcrurn ofsaid strip being substantially at said second line.

6. A contact carrying blade for a thermostat, comprising, a resilient strip of metal having a mounting cnd and a contact end, said mounting end adapted to be fastened in a stack of a thermostat for co-operation therewith, said strip being bent in a first direction to a permanent set of a smll angle along a first line adjacent said mounting end, a circular aperture in the micl-portion of said stripadapted to receive and position the tongue of an insulator spacer button, said strip having a U-shaped slot surrouncling approximately one half of said aperture and positioned substantially symmetrically on the side of said aperture toward said contact end, a U-shaped secondary resilient member lying between said aperture and said slot, said strip being bent in Lhe opposite direction to a permanent set of a second small angle along a second line at about said aperture, said last mentioned permanent set excluding said U-shaped member, said spacer button adapted to be abutted by an adjustable member to place an adjustable load on said U-shaped men1ber in said opposite direction to band said U-shaped member substantially about said second line and thus bend said strip about said first line, said contact end of said strip adapted to l1ave an adjustable load placed thereon in said first direction With the fulcrum of said strip being substantially at said second line.

7. A contact carrying blade for a thermostat, comprising, a resilient strip of metal having a mounting end and a contact end, said mounting end adapted to be fastened in a stack of a therrnostat for co-operation therewith, said strip being bent in a first direction to a permanent set of approximately 15 along a first line adjacent said mounting end, a circular aperture in the miclportion f said strip adapted t0 receive and position the tongue of an insulator spacer button, said strip having a U-shaped slot surrounding approximately 200 cf said aperture and positioned symmetrically 011 the side of said aperture toward said contact end, a U-shaped secondary resilient mernber lying between said aperture and said slot, said strip being bent in tl1e opposite direction to a permanent set of approximately 5 along a second line at about said aperture, said last mentionecl permanent set excluding said U-shapecl member, said spacer button adapted to be abutted by an adjustable mernber t0 place an adjustable load 011 said U-sl1aped member in said opposite direction to bend said U-shaped mernber about said second line and thus bend said strip about said first line, said contact end of said strip adapted to have an adjustable load placed there0n in said first direction With the fulcrurn of said strip being substantially at said second line.

S. A thern1ostat including a base, a resilient strip l1av ing, a fixed end carried by said base, a contact end 011 said strip opposite said fixed end, temperature responsive rneans to engage and deflect said contact end in a given direction, a secondary resilient member cennected to said strip, and adjustable rneans 0n said thermostat disposed to deflect said secondary resilient rnember of said strip in the opposite direction and hence cleflect said strip.

9. A thermostat including a base, a resilient strip having a fixed end carried by said base, a contact end on said strip opposite said fixed end, birnetallic means to engage and deflect said contact end in a given direction, a secondary resilient mernber 011 said strip at about the mid-point thereof, both said strip and said mernbsr having a generally linear relationship o-f force versus deflection, a-djustable means 011 said thern1ostat disposed to deflect said secondary resilient men1ber of said strip in the opposite direction, said secondary resilient member upon deflection causing deflection a lesser degree of said strip.

10. A thermostat including a base, a resilient strip having a. fixed end carried by said base, a contact end 011 said strip opposite said fixed end, bin1etallic rneans to deflect said contact end in a given direction, a seco-ndary resilient men1ber on said strip at ab0nt tl1e mid-point thereof, adjustable means 011 said thermostat disposed to deflect said secondary resilient men1ber of said strip in the opposite direction, said secondary resilient men1- ber upon deflection causing deflection t0 a lesser degree 0f said strip, said secondary resilient member being formed integrally with said strip by a curved slot in said strip.

11. A thermostat including a base, a prin1ary resilient member having a fixed end carried by said base, a coutact end on said member, temperature responsive means to deflect said contact end in a given direction, a secondary resilient rnember attached to said primary member intermediate said ends, a third men1ber having a fixed end carried by said base, spacer means disposed between said third member and said secondary resilient member, and means to deflect said third member in the opposit direction and hence defleet said secondary resilient men1- ber and thus said primary resilient member.

12. A thermostat including a base, a resilient strip having a fixed end carried by said base, a contact end on said strip, temperature responsive means t0 deflect said contact end in a given direction, a secondary resilient rnember 011 said strip at about tl1e mid-point thereof, a second strip having a fixed end carrled by said base, spacer means CllS posed between said second strip and said secondary re silient member, and adjustable means on said thermostat dispesecl to deflect said second strip in tl1e opposite direction and hence deflect said secondary resilient member and thus said resilient strip.

13. A thern1ostat including a base, a resilient strip having a fixed end carried by said base, a contact end on said strip opposite said fixed end, means to deflect said contact end in a given direction, a secondary resilient men1ber 011 said strip at abut the micl-point thereof, a second strip having a fixed end carried by said base, spacer means disposed between said second strip and said secondary resilieni. men1ber, adjustable means 011 said thermostat disposed to deflect said second strip in the opposite direction and hence deflect said secondary resilient mernber, said secondary resilient member upon deflection causing cleflection to a lesser degree cf said resilient strip, and said secondary resilient mernber being formed integrally With said strip by a curved slot in said resilient strip.

l4. A thermostat inelucling a base, a resilient strip having a fixed end carried oy said base, a c0nhct end 011 said strip opposite said fixecl end, birnetallic n1eans to deflect said contact end in a given direction, a secondary resilient n1ernber on said strip at about the n1id-point thereef, a snap acting seccnd strip having a fixed end carried by said. base, a contact end 0n said second strip positionecl to electrically contaet the contact end of said resilient strip, rigid spacer n1eans disposed beaween a n1id-portion 0f said second slrip and said secondary resilient mernoer, adjustable means on said thern1ostat disposed to deflect ehe midportion of said second strip in the opposite direction and hence directly defiect said secondary rcsilient me1nner, said .secondary resilient men1ber upon defiection causing deflection to a lesser degree of said resilient strip, and said secondary resilient member being forrned integrally With said strip by a curved slot in said resilient strip.

15. In a thermostat, a resilient strip cf metal l1aving a mounting end and a working end, said mounting end adaptecl to be fastened in a stack of a thern1osiat for cooperation therewith, a secondary resilient member c0nnected to said strip, both said strip and said member having a generally linear relaticnship 0f f01ce versus cleflection, first means to deflect said seeondary men1ber in a first direction and tl1us deflect said strip in said firsl direction about said mounting end, and second means t0 deflect the worl ing end of said strip in the opposite directi0n to thus deflect said strip in said opposite direction about said mounting end.

16. In a therrnnstat, a resilient strip 0f metal having a mounting end and a contact end, said mounting end adapted to be fastened in a staek cf a therrnostat for cooperation therewith, a secondary resilient member con nected generally at the rnid-portion of said strip, both said strip and said n1ember having a generally linear relationship of force versus deflection, said secondary resilient mernber adapted to be abutted by an adjustable member to place an adjustable load on said secondary n1ember in a first direction to bend said secondary n1ember and thus bend said strip about said mounting end, said contact end of said strip adapted to have an adjustable load placed thereon in the opposite direction With the fulcrum of said strip being substantially at said adjustable member.

References Cited in the file of this patent UNITED STATES PATENTS 2440025 Singleton Apr. 20, 1948 

